Deuterium oxide, reaction

The fact that an isotope effect of 1.7 0.1 is observed 38) in the benzene/deuterium oxide reaction at 30°C indicates that this reaction is the rate-determining step of the dissociative n complex substitution mechanism. In this respect the result agrees with the direct observations made by other investigators 41, 42), namely that unsaturated hydrocarbons chemisorb at a faster rate than their subsequent interactions with chemisorbed hydrogen. 

The slightly different physical properties of deuterium allow its concentration in ordinary hydrogen (or the concentration of a deuterium-containing compound in a hydrogen compound) to be determined. Exchange of deuterium and hydrogen occurs and can be used to elucidate the mechanism of reactions (i.e. the deuterium is a non-radioactive tracer). Methanol exchanges with deuterium oxide thus ... 

The mechanism and the stereochemistry of the reaction was studied using borodeuteride andfor deuterium oxide (480) and a reaction pathway was suggested (Scheme 93). 

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

The NMR spectra of pyrido[2,3-d]pyridazine Af-oxides reduced derivatives and quaternary salts have also been studied and alkaline deuterium exchange reactions investigated <77BSF919). 

A solution of 5a-pregn-9-en-12-one (36, 29 mg) in methanol-OD (5 ml) is saturated with 20% sodium deuterioxide in deuterium oxide and heated under reflux for 3 days. After cooling, the reaction mixture is diluted with ether... 

A solution of estradiol (38, 15 mg) in methanol-OD (4 ml) and one drop of 10% deuteriosulfuric acid in deuterium oxide is heated under reflux for 5 days. After cooling the reaction mixture is diluted with ether, washed with dilute sodium bicarbonate solution and water, then dried over anhydrous sodium sulfate. Evaporation of the ether gives crystalline 2,4-d2-estradiol (39, 15 mg, 99%), mp 173-175° (ether-hexane), exhibiting 82% isotopic purity and only one aromatic hydrogen by NMR. (For an experimental procedure describing the exchange of aromatic protons under Clemmensen conditions, see section III-D.)... 

The earliest attempts to prepare deuterated steroids were carried out by exchange reactions of aliphatic hydrogens with deuterium in the presence of a surface catalyst. Cholesterol, for example, has been treated with platinum in a mixture of deuterium oxide and acetic acid-OD, and was found to yield... 

A solution of the ketone (10 mg) in dry dioxane (5 ml) is placed in the cathode compartment of the cell. Then 10% deuteriosulfuric acid in deuterium oxide (5 ml) is added slowly with stirring. A small additional quantity of dioxane may be necessary to maintain a homogeneous solution. The anode compartment is filled with an identical solvent mixture and the electrode inserted. The current is adjusted to 1(X) milliamps and the electrolysis is continued for 6-10 hr with rapid stirring. The progress of the reaction is... 

During the course of these mechanistic studies a wide range of possible applications of this reaction have been revealed. When the reduction is carried out with lithium aluminum deuteride and the anion complex decomposed with water, a monodeuterio compound (95) is obtained in which 70% of the deuterium is in the 3a-position. Reduction with lithium aluminum hydride followed by hydrolysis with deuterium oxide yields mainly (70 %) the 3j5-di-epimer (96), while for the preparation of dideuterio compounds (94) both steps have to be carried out with deuterated reagents. ... 

Deuterioammonia (about 5 ml) is generated by adding deuterium oxide (14 ml) to a stirred suspension of magnesium nitride (20 g) in mineral oil (30 ml). Tlie deuterioammonia is collected directly in the reaction flask (equipped with a dry ice condenser) at —79° after passing through a trap which is kept at 0°. 

Displacement of aromatic halogen in 2,4-diiodo-estradiol with tritiated Raney nickel yields 2,4-ditritiated estradiol. Aromatic halogen can also be replaced by heating the substrate with zinc in acetic acid-OD or by deuteration with palladium-on-charcoal in a mixture of dioxane-deuterium oxide-triethylamine, but examples are lacking for the application of these reactions in the steroid field. Deuteration of the bridge-head position in norbornane is readily accomplished in high isotopic purity by treatment of the... 

Zinc dust (35 mg) is added to a solution of 9a-bromo-5a-androstan-ll-one (225, 13 mg) in anhydrous ether (2 ml) and acetic acid-OD (0.5 ml, prepared by heating an equimolar mixture of acetic anhydride and deuterium oxide) and the resulting suspension is stirred at room temperature for 4 hr. (The progress of the reaction can be checked by thin layer chromatography.) The... 

Trimethyl borate (113 ml) is added dropwise to 66 ml of deuterium oxide (exothermic reaction). The mixture is allowed to stand for 1/2 hr and the precipitated boric acid-d3 is removed by filtration. Sodium methoxide is... 

Dimethyl sulfate (16 g) is added to a mixture of dimethyl carbonate (400 g) and deuterium oxide (1(X) g) in a 1 liter flask. Two reflux condensers and a drying tube are attached in series (initial rapid evolution of carbon dioxide may entrain some liquid), and the reaction mixture is heated under reflux for 72 hr. The methanol-OD is distilled directly from the reaction flask through a 30 cm Vigreux column. Redistillation from a small amount of sodium yields 275 g of pure methanol-OD bp 66-66.5° isotopic purity, 98.6%. ... 

Tetraethyl orthosilicate (104.2 g) and deuterium oxide (40 g) are stirred in a stoppered distillation flask at room temperature until a viscous, miscible solution is obtained (approximately 24 hr). (A small amount of acid catalyst, such as deuteriochloric acid, speeds up the reaction considerably. ) A distillation head and a receiver cooled in a dry ice-acetone bath are attached and the solution is distilled at 2 mm pressure until no further product is obtained. A 90% yield of ethanol-OD is obtained having an isotopic purity equal to that of the deuterium oxide used. ... 

Deuterium oxide (7.5 ml) is added dropwise to aluminum isopropoxide (25 g.) The mixture is shaken for about 5 min and then warmed to 70° for 10 min to complete the reaction. The resulting deuterioisopropanol is distilled at room temperature and 1 mm pressure into a liquid nitrogen-cooled trap. Redistillation at atmospheric pressure yields pure isopropanol-OD (9.5 g bp 82-83°). All operations must be protected from moisture. 

Deuterio-3-iiitro-l,6-iiaphthyridiiie (168) was prepared from 4-chloro-3-iiitro-l,6-iiaphthyridiiie (166) by a reaction with tosyl hydrazide and subsequent hydrolysis of the 4-tosylhydrazino derivative (167) with Na2C03/ D2O solution (83RTC359). 7-Deuterio-l,8-naphthyridin-2(lH)-one was prepared by heating l,8-naphthyridin-2(lH)-one with deuterium oxide at 230°C for 35 h (85JHC761). Tliis deuterio compound could be converted into 2-chloro-(or 2-ethoxy-) 7-deuterio-3,6-dinitro-l,8-naphthyridine. 

However, such an explanation was not convincing for other authors. Maeda and Kojima found that the irradiation of 2-phenylthiazole in ethanol at 80°C led to the same products described before but in a different ratio. Under the same reaction conditions, 5-phenylthiazole gave 4-phenylisothiazole, while 4-phenyl-thiazole was converted into 3-phenylisothiazole. The most important observation those authors made was that deuterium incorporation occurred when the reaction was carried out in benzene at 80°C in the presence of deuterium oxide. In fact, 2-phenylthiazole furnished deuterated 3-phenyl-4-deuteroisothiazole and... 

In neutral and alkaline media, the rate of exchange at the 3 and 6 position of 4-aminopyridazine is independent of acidity but decreases markedly when the media become more acidic. This was interpreted in terms of a rate-determining removal of the 6-proton by deuteroxide ion to give the ylid (XXIV), which reacts with deuterium oxide in a fast step. A similar result for the 3 and 6 positions of py-ridazin-4-one suggests the same mechanism. For reaction at the 5 position, the rate-acidity profile indicated reaction on the free base as did that for the 5 position of pyridazin-3-one, though the appearance of a maximum in the rate at — HQ = 0.8 was anomalous and suggested incursion of a further mechanism. 

Heavy water is deuterium oxide, D20. The standard reaction Gibbs free energy for the autoprotolysis of pure deuterium oxide is +84.8 kj-mol 1 at 298 K. (a) If pD is defined analogously to pH, what is the pD of pure D20 at 298 K ... 

The decarboxylation of carboxylic acid in the presence of a nucleophile is a classical reaction known as the Hunsdiecker reaction. Such reactions can be carried out sometimes in aqueous conditions. Man-ganese(II) acetate catalyzed the reaction of a, 3-unsaturated aromatic carboxylic acids with NBS (1 and 2 equiv) in MeCN/water to afford haloalkenes and a-(dibromomethyl)benzenemethanols, respectively (Eq. 9.15).32 Decarboxylation of free carboxylic acids catalyzed by Pd/C under hydrothermal water (250° C/4 MPa) gave the corresponding hydrocarbons (Eq. 9.16).33 Under the hydrothermal conditions of deuterium oxide, decarbonylative deuteration was observed to give fully deuterated hydrocarbons from carboxylic acids or aldehydes. 

The stereochemistry of dienes has been found to have a pronounced effect in the concerted cyclo-additions with benzyne 64>65h A concerted disrotatory cyclo-addition of tetrafluorobenzyne, leading for example with trans- (3-methylstyrene to (63, R = Me), is likely and in accord with the conservation of orbital symmetry 68>. However while the electro-cyclic rearrangement of (63, R = H) to (65, R = H) is not allowed, base catalysed prototropic rearrangement is possible. A carbanion (64, R = H) cannot have more than a transient existence in the reaction of tetrafluorobenzyne with styrene because no deuterium incorporation in (65) was detected when either the reaction mixture was quenched with deuterium oxide or when the reaction was conducted in the presence of a ten molar excess of deuteriopentafluorobenzene. 

When we allowed pentafluorophenyl-lithium to decompose in ether in the presence of an excess of N, ZV-dimethy laniline we obtained the compounds (92) 70, X = F), (94), the latter as the major compound, and a product which was shown to be (97). That this latter compound did not arise by metallation of 2V,lV-dimethylaniline followed by addition to tetrafluorobenzyne was shown by quenching the reaction mixture with deuterium oxide. No deuterium incorporation was detected. The compound (97) provides a rare example of a product derived by a Stevens rearrangement in which aryl migration has occurred b>. 

The mechanism of this unusual dimerization is not known. All the lithiumorganic compounds have been identified by the reaction with dimethyl sulfate as well as by deuterolysis with deuterium oxide. 

B. Reactions of Benzene with Deuterium Oxide and with Deuterium-... 

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